Here's something up for casual discussion.
I found an old and cheap filter in my dry cab and decided to test it against
my A850 (24 megapixel full frame camera) with a CZ 16-35mm (arguably one of the best wide angle lenses)
Below are two set of images, 100% crop, one with and one without the cheap $10 filter. Pictures are straight out of camera and 100% center crop.
Shot at F2.8
Shot at F8
Can you tell which is which?
(sorry for the difference in size for the 1st set, forgot to turn off auto resize when uploading, but I suppose it didn't resize it too much so i didn't bother to upload again..)